1. Field of the Invention
This invention relates to a navigation device that can display dynamic travel information. Dynamic travel information is updated information about road driving and traffic conditions, such as information about congestion, road blocks, adverse weather etc. on particular routes. The information is dynamic in the sense that it can change. The information displayed on the device is ideally completely up to date, although in practice there is some time delay between observing and reporting on road and traffic conditions and receiving those reports at the device. The device finds particular application as an in-car navigation system.
2. Description of the Prior Art
GPS based navigation devices are well known and are widely employed as in-car navigation systems. Reference may be made to the Navigator series software from the present assignee, TomTom B.V. (now TomTom International B.V.). This is software that, when running on a PDA (such as a Compaq iPaq) connected to an external GPS receiver, enables a user to input to the PDA a start and destination address. The software then calculates the best route between the two end-points and displays instructions on how to navigate that route. By using the positional information derived from the GPS receiver, the software can determine at regular intervals the position of the PDA (typically mounted on the dashboard of a vehicle) and can display the current position of the vehicle on a map and display (and speak) appropriate navigation instructions (e.g. ‘turn left in 100 m’). Graphics depicting the actions to be accomplished (e.g. a left arrow indicating a left turn ahead) can be displayed in a status bar and also be superimposed over the applicable junctions/turnings etc in the roads shown in the map itself. Reference may also be made to devices that integrate a GPS receiver into a computing device programmed with a map database and that can generate navigation instructions on a display. The term ‘navigation device’ refers to a device that enables a user to navigate to a pre-defined destination. The device may have an internal system for receiving location data, such as a GPS receiver, or may merely be connectable to a receiver that can receive location data.
Reference may be made to U.S. Pat. No. 5,612,881, which shows an in-car navigation device that can display a schematic representation of the entire journey and can display estimated arrival times at various points on the journey. Dynamic travel information is not however included in the display at all. Superimposing dynamic travel information onto a navigation map is however known from U.S. Pat. No. 5,831,552, U.S. Pat. No. 5,694,122 and U.S. Pat. No. 5,864,305.
In-car navigation systems may have access to real-time updated travel information; for example, in the Smartnav™ system from TrafficMaster plc, a central server receives real time updated traffic information from sensors located by the roadside of the UK road network. The server calculates routes to be followed, given a driver's start and destination address, and sends that route information to an in-vehicle device which speaks appropriate instructions to the driver (hence, there is no map display as such). When congestion etc. is spotted that is relevant to a particular driver's route, the server can send a message to that driver's navigation device, which is then relayed as an audio alert to the driver.
Superimposing dynamic travel information onto a navigation map generated and displayed by an in-car navigation device is also known from U.S. Pat. No. 5,831,552, U.S. Pat. No. 5,694,122 and U.S. Pat. No. 5,864,305.